Natural language processing (NLP) is a technique that facilitates exchange of information between humans and data processing systems. For example, one branch of NLP pertains to answering questions about a subject matter based on information available about the subject matter domain.
Information about a domain can take many forms and can be sourced from any number of data sources. The presenter of the information generally selects the form and content of the information. Before information can be used for NLP, generally, the information has to be transformed into a form that is usable by an NLP engine.